GB190005737A - Improvements in Appliances for Adjusting and Working the Shutters and Diaphragms of Photographic Cameras. - Google Patents

Abstract

5737. Watkins, A. March 27. Exposures, determining; shutters; lens fittings.- Relates to a shutter combined with a slide-rule by which the time of exposure is calculated from the necessary data, namely, size of diaphragm, sensitiveness of plate, and intensity of light. The sensitiveness of the plate, and the intensity of light, are represented on two movable logarithmic scales a and b. The figures representing these factors in the particular case are first brought into coincidence by moving one of the scales, and then both scales are moved together until the index points on a and b indicate the required diaphragm aperture and time of exposure. The slide a is connected to a rack which gears with a pinion fixed to the diaphragm plate, and thus brings the required aperture opposite the centre of the lens; or the diaphragm may be set by hand. The slide b is connected to a rod m, which is tapered so as to regulate the exit from the cylinder of an air brake by which the speed of the shutter is regulated. The shutter consists of two spring-actuated sectors o, c, one of which o opens the lens, and the other c closes it, both being simultaneously released by pressing the button w against the lever x. The time which elapses before the sector c closes the lens is controlled by the air piston which is geared to the sector by the rack h and pinion i.